Rotary engines, such as for example Wankel engines, use the eccentric rotation of a piston to convert pressure into a rotating motion, instead of using reciprocating pistons. In these engines, the rotor includes a number of apex or seal portions which remain in contact with a peripheral wall of the rotor cavity of the engine throughout the rotational motion of the rotor to create a plurality of rotating cavities when the rotor rotates.
In Wankel engines, the inlet and exhaust ports are usually designed mechanically to allow a minimum overlap between them during the intake and exhaust portions of the cycle, such as to purge the exhaust cavity of combustion gases prior to re-filling the intake cavity with a fresh supply of air. Failure to purge the exhaust cavity of the combustion gases may result in a reduction in cycle volumetric efficiency. However, overlap of the ports may limit the range of volumetric compression ratio that can be obtained. Therefore, the need remains for improvement in optimizing how rotary engines may be operated.